Insolubilizing agent for specific toxic substances, method for insolubilizing specific toxic substances using same, and soil improving method

ABSTRACT

Provided is a practically valuable and economically excellent insolubilizing material for a specific toxic substance: that is useful for insolubilizing treatment for a heavy metal or the like conducted by applying the insolubilizing material for a specific toxic substance to soil or on the surface of the soil; that is capable of effectively insolubilizing and immobilizing the heavy metal or the like; that is capable of making treated matter neutral so as to be reusable and environment-friendly; and moreover that is capable of imparting strength to the treated matter as necessary; and with which the heavy metal or the like is not re-eluted even when the treated matter is exposed to an environment under a neutral condition or an acidic condition. An insolubilizing material for a specific toxic substance to be used so that soil does not reach a strongly alkaline region of a pH of 11 or more, wherein the insolubilizing material for a specific toxic substance comprises an amorphous aluminum compound or a derivative thereof as a main component, or an insolubilizing material for a specific toxic substance to be used so that soil containing a heavy metal or the like does not reach a strongly alkaline region of a pH of 11 or more, the insolubilizing material for a specific toxic substance functioning also as a solidifying material, wherein the insolubilizing material for a specific toxic substance comprises gypsum obtained by adding and mixing, to the gypsum, the amorphous aluminum compound and the derivative thereof in a range of 0.5 to 60 mass parts relative to 100 mass parts of the gypsum, and a method for improving soil using the insolubilizing material for a specific toxic substance.

TECHNICAL FIELD

the present invention relates to an economically excellentinsolubilizing material for a specific toxic substance (hereinafter,also referred to as “heavy metal or the like”). Specifically, the firstinvention of the present invention relates to an insolubilizing materialfor a specific toxic substance (heavy metal or the like) capable ofinsolubilizing a specific toxic substance (heavy metal or the like)contained in soil such as soil at a site of an abolished plant and soilfor landfill and suppressing re-elution of the specific toxic substance(heavy metal or the like) from treated matter, and also relates to amethod for insolubilizing a specific toxic substance (heavy metal or thelike) using the insolubilizing material for a specific toxic substance(heavy metal or the like). The second invention of the present inventionrelates to an insolubilizing material for a specific toxic substance(heavy metal or the like): comprising gypsum as an essential component;being useful particularly for treatment of soil to which soil thefluidity is imparted by adding mud and water thereto; in addition to theabove effects, being capable of imparting, to treated matter, strengththat is about the same as or more than the strength with which handlingduring transportation and landfill can easily be carried out; andfunctioning as a solidifying material, and also relates to a method forimproving soil using the insolubilizing material for a specific toxicsubstance.

BACKGROUND ART

a case may exist that contaminated soil contaminated by a heavy metal orthe like is present at a site or the like of an abolished plant that hasbeen in operation since the times when the health hazards due to theheavy metal or the like were not recognized. Moreover, the heavy metalor the like may also be contained in surplus soil for landfill due tothe contaminated soil. In recent years, it has been known that the heavymetal or the like contained in such soil is eluted and intrude intoground water to cause a situation that threatens human health, and theimportance of the technology to stably immobilize the heavy metal or thelike in soil or the like has been recognized. Moreover, since alkalinesoil mixed with mortar by a shield construction method at a constructionsite are frequently discharged for example, the surplus soil to be usedfor landfill is often alkaline. Against this problem, it is desired thatthe filled-up soil be neutral from the consideration to environment.Moreover, the surplus soil to be used for landfill such as large amountof sludge generated by waste water treatment and surplus soil waste fromconstruction often has high water content ratio, and in the case wheresuch soil is used for landfill, it often becomes necessary to solidifythe mud. Moreover, in Japan where there are many volcanoes and that issurrounded by sea, the heavy metal or the like may be contained innatural strata and soil, and soil in the coastal area, and there is acase where insolubilization of the heavy metal or the like is needed insoil near the living space such as a residential area and a river-headarea.

As described previously, since the need for preventing the elution ofthe heavy metal or the like from the soil at the site or the like of anabolished plant, or soil filled up with surplus soil has beenrecognized, the various types of insolubilizing materials for a heavymetal or the like have conventionally been used for the purpose ofsuppressing the elution of the heavy metal or the like, and the effectsthereof have been confirmed. In addition, the “heavy metal or the like”in the present invention means that the “Heavy Metal or the like beingDesignated Hazardous Substance (class II specified chemical substance)”specified in Article 2 of Soil Contamination Countermeasures Act thatcame into effect in 2003, and specifically denotes the followingcompounds.

Cadmium and compounds thereof

Hexavalent chromium compounds

Cyanides

Mercury and compounds thereof (including alkyl mercury compounds)

Selenium and compounds thereof

Lead and compounds thereof

Arsenic and compounds thereof

Fluorine and compounds thereof

Boron and compounds thereof

However, a case may exist that the conventional insolubilizing materialfor a heavy metal or the like needs solidifying treatment (impartingstrength) separately because some treated matter after insolubilizingtreatment comes into a state where the handling during transportation orlandfill carried out after the insolubilizing treatment becomesdifficult. On the other hand, cement based or lime based solidifyingmaterials have generally been used for solidifying treatment of soil,however there is a problem that the soil after treatment showsalkalinity due to the use of the solidifying materials. Namely, thedevelopment of a solidifying material that makes the soil (treatedmatter) after treatment neutral from the consideration to environment isdesired when it is taken into consideration that the treated mattertreated with the above-described solidifying materials is used forlandfill or the like after the treatment.

Here, there exists a method of utilizing a neutral gypsum basedsolidifying material as a method for conducting soil solidification in aneutral pH, however there is a problem that the treated matter isinferior in strength. Against this problem, a method of enhancing thestrength of the treated matter by adding an aluminum compound and acalcium compound so as to generate ettringite when the solidifyingmaterial is mixed with the soil (see, Patent Literature 1). Furthermore,studies on utilizing, as a raw material for a cement basedinsolubilizing material, recycled gypsum that is separated and recoveredfrom a waste gypsum board being a construction waste material, recycledgypsum that is derived from a waste gypsum mold, or the like(hereinafter, abbreviated as “waste gypsum”) derived from recycledgypsum) have been made for the purpose of promoting recycling of aconstruction material. However, there may be a case that a heavy metalor the like such as fluorine and lead derived from the waste gypsumitself or another dismantled construction material mixed into the wastegypsum is contained in the waste gypsum. Therefore, there is a risk,attributable to the above-described case, that a situation where theelution amount of the heavy metal or the like exceeds the environmentalstandard value is brought about by using the gypsum based solidifyingmaterial utilizing waste gypsum. Since it is the biggest technologicalproblem in the solubilizing material for a specific toxic substance tomore effectively suppress the elution of the heavy metal or the like inthe mud being an object of treatment and reduce the amount of theelution thereof, the occurrence of the above-described situation must beavoided even in the case where the heavy metal or the like derived fromwaste gypsum is present, and the development of an insolubilizingmaterial for a heavy metal or the like having a higher effect isdesired.

Under the above-described circumstances, as a method for making fluorinehardly soluble and stable against fluorine polluted soil or the like,for example, a method for making fluorine hardly soluble and stable bygenerating fluorinated apatite and ettringite with a material containinggypsum, lime, ferrous sulfate, and a phosphate compound has beenproposed (see, Patent Literature 2). Moreover, the present applicantshas so far made a proposal on a gypsum based insolubilizing andsolidifying material for a heavy metal or the like, the gypsum basedinsolubilizing and solidifying material for a heavy metal or the like:capable of making the treated matter neutral; capable of insolubilizinga heavy metal or the like contained in the mud, and at the same timesolidifying the heavy metal or the like, and imparting the strength tothe mud to make the mud excellent in handling (see, Patent Literature 3)by using the gypsum based insolubilizing and solidifying material for aheavy metal or the like with the gypsum based insolubilizing andsolidifying material for a heavy metal or the like mixed and added inthe sludge generated by waste water treatment or the mud such asconstruction surplus soil. Specifically, the proposal on aninsolubilizing and solidifying material for a heavy metal or the like inwhich an aluminum compound selected from aluminum hydroxide and so onand a neutralizing agent containing a calcium or magnesium component arecontained in calcined gypsum has been made.

In contrast with the above-described development of the solidifyingmaterial, the development of a new material different from theconventional cement based, lime based, or gypsum based solidifyingmaterial is also progressing. For example, a method of utilizinghydraulic alumina, as a neutral solidifying material forwater-containing soil suitable for solidifying water-containing soilsuch as dredged bottom mud and construction sludge, the hydraulicalumina produced through oxidation treatment by heating an aluminumcompound comprising, as a main component, amorphous aluminum hydroxideproduced as a by-product by neutralization and aggregation in a step ofpositive electrode oxidation treatment of aluminum has been proposed(see, Patent Literatures 4 and 5). It is taken in these literatures thatwater-containing soil can be solidified in a neutral state so as to havea sufficient strength by allowing the hydraulic alumina to contain aninsolubilizing assistant (solidification strength-enhancing agent) suchas lithium carbonate and calcium carbonate. Moreover, it is also takenin these literatures that the elution of a heavy metal such ashexavalent chromium can be prevented.

CITATION LIST Patent Literature Patent Literature 1: JP-A-2009-51910Patent Literature 2: JP-A-2007-330884 Patent Literature 3:JP-A-2010-207659 Patent Literature 4: JP-B-4690729 Patent Literature 5:JP-B-4680549 SUMMARY OF INVENTION Technical Problem

However, the technology described in Patent Literature 1 does not intendto insolubilize a heavy metal or the like, moreover since the generationof ettringite that contributes to enhancing the strength of the treatedmatter occurs in a strongly alkaline region, even if an assumption ismade that there is a possibility that the heavy metal or the like isimmobilized in the generated ettringite, there is a possibility thatettringite is decomposed under an acidic condition such as an acid rainto re-elute the heavy metal or the like.

In the same way, since fluorine is made hardly soluble and stable bygenerating ettringite in the technology described in Patent Literature2, it is necessary to keep the pH alkaline, and therefore there has beena problem that the treated matter does not become neutral. Moreover,there is another problem that it is necessary to adjust the compositionof the insolubilizing material according to the pH of the soil in themethod of utilizing an acidic material and an alkaline material bymixing them as described in Patent Literature 2.

Moreover, neutral treated matter is obtained in the technology describedin Patent Literatures 3 to 5, however the main object thereof is tosolidify the mud, and there has been room for improvement from thestandpoint of realizing more effective insolubilization of the heavymetal or the like and stable immobilization of various types of heavymetals and so on for a long period of time. For example, even though thelow-cost gypsum is used as a raw material in Patent Literature 3, theneutralizing agent comprising an aluminum compound and a calcium ormagnesium component is necessary, and therefore there is a problem fromthe stand point of providing a lower-cost and surer treatment method.

Moreover, although the raw material for obtaining hydraulic alumina isamorphous aluminum hydroxide produced as a by-product by neutralizationand aggregation in the step of positive electrode oxidation treatment ofaluminum in the technology described in Patent Literatures 4 and 5, itis required to conduct oxidation treatment by heating amorphous aluminumhydroxide, and therefore there is a big problem from the standpoint ofeconomy of conducting treatment to a large amount of soil more surelywith lower cost. Moreover, the hydraulic alumina has been developed as asolidifying material, it is hard to say that the hydraulic alumina issufficient in terms of insolubilizing a heavy metal or the like, andthere is also room for improvement in terms of this point.

Furthermore, as described below, there has been room for improvement inany of the technologies in terms of more surely achieving of stablyimmobilizing the heavy metal or the like that is immobilized in thetreated matter for a long period of time in the treated matter that isused for landfill and is to be left in various environments in additionto more efficiently insolubilizing various types of the heavy metals andso on. Namely, according to the studies made by the present inventors,it has been hard to say that the current technologies can sufficientlyand surely achieve the performance in terms of stably maintaining afurther desired state where the heavy metal or the like that isinsolubilized in the treated matter is stably insolubilized withoutre-elution against the acid rain even though the heavy metal or the likecontained in the soil can be insolubilized and, as necessary, solidifiedto impart strength to the soil with the current technologies.

Moreover, it is considered that much of the heavy metal or the like ispresent near the surface of the polluted soil particularly at the siteor the like of an abolished plant, so an insolubilizing material for aheavy metal or the like capable of immobilizing the heavy metal or thelike by just spraying the insolubilizing material for a heavy metal orthe like to apply on the surface of the soil with which insolubilizingmaterial for a heavy metal or the like treatment becomes simple isextremely useful when developed.

Therefore, an object of the present invention is to provide a highperformance insolubilizing material for a specific toxic substance(heavy metal or the like) in which the problems of the above-describedconventional technologies are solved. Namely, an object of the presentinvention is to provide an economical insolubilizing material for aspecific toxic substance capable of using a low-cost raw material ininsolubilizing treatment conducted by adding and mixing aninsolubilizing material to soil or insolubilizing treatment conducted byspraying an insolubilizing material on the surface of the soil, theinsolubilizing material: capable of effectively insolubilizing andimmobilizing a heavy metal or the like that is present in the soil ornear the surfaces of the soil and gives influence on human health;capable of making treated matter neutral so as to be reusable andenvironment-friendly; furthermore without the re-elution of the heavymetal or the like even in the case where the treated matter is exposedto a neutral condition or acidic condition such as an acid rain; andtherefore being practically valuable. Particularly, it is extremelyuseful when the waste the treatment of which has conventionally been aproblem can be used as a raw material, and another object of the presentinvention is to provide an insolubilizing material for a specific toxicsubstance that is also extremely useful economically.

Furthermore, an object of the second present invention is to provide apractically valuable insolubilizing material for a specific toxicsubstance the treated matter of which is imparted strength and is easyto handle in soil treatment in addition to the above-described effects.

Solution to Problem First Invention of Present Invention

The above-described objects can be achieved by the present invention.Namely, the first invention of the present invention provides aninsolubilizing material for a specific toxic substance to be used sothat soil does not reach a strongly alkaline region of a pH of 11 ormore, wherein the insolubilizing material for a specific toxic substancecomprises an amorphous aluminum compound or a derivative thereof as amain component, or, as an insolubilizing material having anotherconstitution, an insolubilizing material for a specific toxic substanceto be used so that soil does not reach a strongly alkaline region of apH of 11 or more, wherein the insolubilizing material for a specifictoxic substance comprises an amorphous aluminum compound or a derivativethereof as a main component and further comprises a calcium componentexhibiting acidity, neutrality, or weak alkalinity of a pH of less than11 when the calcium component makes contact with moisture contained inthe soil.

Moreover, preferable embodiments of the first present invention of thepresent invention include that: the amorphous aluminum compound isamorphous aluminum hydroxide; the amorphous aluminum compound or thederivative thereof is derived from aluminum sludge and is to be used asit is, or obtained by dehydrating and drying, without changing theproperties, an amorphous aluminum compound or the derivative thereofderived from aluminum sludge; the specific toxic substance is at leastany one selected from the group consisting of cadmium and compoundsthereof, hexavalent chromium compounds, cyanides, mercury and compoundsthereof (including alkyl mercury compounds), selenium and compoundsthereof, lead and compounds thereof, arsenic and compounds thereof,fluorine and compounds thereof, and boron and compounds thereof; thecalcium component is at least any one selected from the group consistingof gypsum dihydrate, calcium carbonate, calcium peroxide, calciumfluoride, calcium iodide, calcium phosphate, calcium chloride, calciumnitrate, calcium acetate, calcium citrate, calcium gluconate, calciummalate, and calcium lactate.

Furthermore, another embodiment of the first invention of the presentinvention provides a method for insolubilizing a specific toxicsubstance, the method comprising conducting treatment to soil so thatthe soil does not reach a strongly alkaline region of a pH of 11 or moreby adding and mixing, or spraying to the soil the insolubilizingmaterial for a specific toxic substance to insolubilize the specifictoxic substance.

Moreover, the preferable embodiments include: adding and mixing, orspraying to the soil the amorphous aluminum compound or the derivativethereof being a main component of the insolubilizing material for aspecific toxic substance within a range of 0.5 to 50 g per 1 kg on a drymass basis of the soil; and further preferably adding and mixing, orspraying to the soil the amorphous aluminum compound and the derivativethereof being a main component of the insolubilizing material for aspecific toxic substance within a range of 10 to 40 g per 1 kg on a drymass basis of the soil. Moreover, the preferable embodiments include:the specific toxic substance to be insolubilized is attributable to thesoil or a constituent of the insolubilizing material; and theconstituent of the insolubilizing material is a calcium component. Inaddition, the above-described dry mass means the mass of soil that isdried until the mass of the soil becomes a constant weight in a dryingfurnace at 110° C.±5° C. in accordance with “the method for watercontent of soils JIS A1203”.

Second Invention of Present Invention

The above-described objects can be achieved by the following presentinvention. Namely, the second invention of the present inventionprovides an insolubilizing material for a specific toxic substance to beused so that soil containing a specific toxic substance does not reach astrongly alkaline region of a pH of 11 or more, the insolubilizingmaterial for a specific toxic substance comprising calcined gypsum andfunctioning also as a solidifying material, wherein the insolubilizingmaterial for a specific toxic substance comprising calcined gypsum isobtained by adding and mixing, to the calcined gypsum, an amorphousaluminum compound or the derivative thereof in a range of 0.5 to 60 massparts relative to 100 mass parts of the calcined gypsum.

Moreover, the preferable embodiments of the second invention of thepresent invention include the followings. The amorphous aluminumcompound is amorphous aluminum hydroxide; the amorphous aluminumcompound or the derivative thereof is derived from aluminum sludge andis to be used as it is, or obtained by dehydrating and drying, withoutchanging the properties, an amorphous aluminum compound or thederivative thereof derived from aluminum sludge; the insolubilizingmaterial for a specific toxic substance is obtained by adding andmixing, to the calcined gypsum, the amorphous aluminum compound and thederivative thereof in a range of 15 to 50 mass parts relative to 100mass parts of the calcined gypsum; and the specific toxic substance isat least any one selected from the group consisting of cadmium andcompounds thereof, hexavalent chromium compounds, cyanides, mercury andcompounds thereof (including alkyl mercury compounds), selenium andcompounds thereof, lead and compounds thereof, arsenic and compoundsthereof, fluorine and compounds thereof, and boron and compoundsthereof.

Furthermore, another embodiment of the second invention of the presentinvention provides a method for improving soil, comprising conductingtreatment to the soil containing a specific toxic substance so that thesoil does not reach a strongly alkaline region of a pH of 11 or more byadding and mixing to the soil the aforementioned insolubilizing materialfor a specific toxic substance functioning also as a solidifyingmaterial. Moreover, the preferable embodiments include adding and mixingto the soil the insolubilizing material for a specific toxic substancewithin a range of 30 to 200 kg per 1 m³ of the soil containing aspecific toxic substance.

Advantageous Effects of Invention First Invention of Present Invention

According to the first invention of the present invention, in the casewhere the insolubilizing material for a specific toxic substance is usedso that soil does not reach a strongly alkaline region of a pH of 11 ormore, namely, in a pH region where ettringite is not generated, anexcellent insolubilizing material for a specific toxic substance to makethe treated matter in which the heavy metal or the like that is presentin the soil or near the surface of the soil are effectivelyinsolubilized, and in which re-elution of the insolubilized heavy metalor the like is suppressed under both of neutral and acidic conditions isprovided. Moreover, the insolubilizing material for a specific toxicsubstance of the first invention of the present invention is a simpleinsolubilizing material for a specific toxic substance with which theabove-described effects are exhibited not only in the case of a methodof conducting treatment by adding and mixing the insolubilizing materialfor a specific toxic substance to the soil but also just by spraying theinsolubilizing material for a specific toxic substance to the surface ofthe soil. Furthermore, the treated matter is made neutral taking theenvironmental effects into consideration in the case where the treatedmatter is used for landfill or the like. Moreover, according to thepresent invention, aluminum sludge that is generated at an anodizedaluminum plant or an aluminum sash plant, and most of which is taken aswaste can effectively be utilized as the amorphous aluminum compoundthat characterizes the present invention, and therefore it becomespossible to provide an environmental friendly product.

Second Invention of Present Invention

According to the second invention of the present invention, theexcellent insolubilizing material for a specific toxic substance: withwhich the heavy metal or the like is effectively insolubilized; thatmakes the treated matter in which the re-elution of the insolubilizedheavy metal or the like in the treated matter is suppressed under bothof neutral and acidic conditions, and that makes the state of thetreated matter so that the treated matter has the solidificationstrength so as to be easy for handling at the time of transportation orlandfill; and that functions also as a solidifying material in the casewhere the insolubilizing material for a specific toxic substance is usedfor insolubilizing treatment of the heavy metal or the like in the soilor mud under a condition that the soil or mud does not reach a stronglyalkaline region of a pH of 11 or more. Particularly, the treated matterthat is solidified by the insolubilizing material for a specific toxicsubstance is made neutral taking the influence on the environment whenthe treated matter is utilized as it is for landfill or the like.Moreover, according to the second invention of the present invention,aluminum sludge that is generated at an anodized aluminum plant or analuminum sash plant, and most of which is taken as waste can effectivelybe utilized as the amorphous aluminum compound that characterizes thepresent invention and, in addition to this, the calcined waste gypsumcan be utilized as a raw material for gypsum, and therefore the secondpresent invention of the present invention can contribute the solutionto a problem of recycling of a construction waste material, and itbecomes possible to provide a further environmental friendly product.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a measurement result of X-ray diffraction (CuK_(α) line) fordehydrated and dried aluminum sludge.

FIG. 2 is a graph illustrating the measurement results of X-raydiffraction (CuK_(α) line) for collected samples of the soil only, after1 week of curing, and after 1 month of curing respectively when theinsolubilizing material for a specific toxic substance of the presentinvention is mixed with the soil so that the soil does not reach astrongly alkaline region of a pH of 11 or more.

FIG. 3 is a graph illustrating elution test results under a neutralcondition and an acidic condition for each of the treated matter inwhich an insolubilizing material for a specific toxic substance of thepresent invention and a cement solidifying material are usedrespectively.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in more detailgiving preferable embodiments. The present inventors have made detailedstudies as to the reason that the elution of the heavy metal or the likecontained in the soil has not been able to be sufficiently suppressedand further the reason that the solidifying performance has not beenstable when the solidifying function is imparted to the insolubilizingmaterial for a specific toxic substance in the treatment of the soilthat contains a heavy metal or the like in the past in order to solvethe above-described conventional technical problems.

As a result of the studies, the present inventors have found that: theconventional insolubilizing material that has been used for theabove-described insolubilizing treatment of the heavy metal or the likein the soil or mud has insufficient reactivity with the heavy metal orthe like, and therefore there is a problem that the use amount becomeshuge in order to thoroughly insolubilize the heavy metal or the like;and moreover even though the heavy metal or the like is thoroughlyinsolubilized during the treatment, immobilizing the heavy metal or thelike in a state where the heavy metal or the like is stablyinsolubilized has not been achieved and the re-elution of the heavymetal or the like in the case where the treated matter is used forlandfill or the like after treatment may be recognized.

Moreover, as described previously, it often happens that theconventional insolubilizing material or the conventional solidifyingmaterial that is used therewith shows alkalinity in itself, andtherefore is insufficient in terms of environmental friendliness, whichhas been a big factor to make the treated matter difficult to utilize.Furthermore, the present inventors have recognized that there is aproblem that when the treated matter is exposed to an acid conditionsuch as acid rain in particular, the heavy metal or the like that isinsolubilized is re-eluted from the treated matter, and this isremarkable in the case where the treated matter shows alkalinity.Moreover, the present inventors have confirmed that the problem ofre-elution of the heavy metal or the like may occur similarly in theinsolubilizing material for a specific toxic substance that alsofunctions as a solidifying material. Furthermore, it is considered thatmuch of the heavy metal or the like is present near the surface of thepolluted soil particularly at the site or the like of an abolishedplant, so it is extremely useful when an economically excellentinsolubilizing material for a specific toxic substance capable of surelyand stably immobilizing the heavy metal or the like by just spraying theinsolubilizing material for a specific toxic substance to apply on thesurface of the soil is developed. However, such an insolubilizingmaterial has not yet been known.

First Invention of Present Invention

The present inventors have made further detailed studies based on theabove-described findings, and as a result thereof, the present inventorshave achieved the first invention of the present invention. Namely, thepresent inventors have reached the present invention by finding thatwhen the amorphous aluminum compound or the derivative thereof(hereinafter, referred to as the amorphous aluminum compound) inparticular among the aluminum compounds is added and mixed or sprayed tothe soil, it becomes possible to provide the insolubilizing material fora heavy metal or the like: that is capable of more surely and stablyinsolubilizing the heavy metal or the like; further the treated matterof which is stably maintained in a state where the heavy metal or thelike is not re-eluted and is immobilized even in the case where thetreated matter is exposed to an acidic condition such as an acid rain;and that makes the treated matter neutral. In addition, the amorphousaluminum compound and a derivative thereof may be an aluminum compoundwhich is recognized that the aluminum compound is in a state of anamorphous state by X-ray diffraction. Moreover, as will be describedlater, as the amorphous aluminum compound that is used in the presentinvention, the aluminum sludge that is generated from an anodizedaluminum plant or an aluminum sash plant and most of which has beendisposed of can be utilized as it is or in a state obtained byconducting a simple dehydration or air drying, and therefore theinsolubilizing material for a specific toxic substance of the presentinvention becomes extremely economical in its material constitution.

Hereinafter, each material that constitutes the insolubilizing materialfor a specific toxic substance of the first invention of the presentinvention will be described.

(Amorphous Aluminum Compound)

The present inventors consider as follows from the verification resultsdescribed later about the reason that the amorphous aluminum compoundthat characterizes the insolubilizing material for a specific toxicsubstance of the first invention of the present invention has been ableto effectively immobilize the heavy metal or the like in the treatedmatter and also has been able to function as an excellent insolubilizingcomponent that can effectively suppress the re-elution of theimmobilized heavy metal or the like from the treated matter under bothof the neutral condition and the acidic condition. When theinsolubilizing material for a specific toxic substance or the like ofthe present invention is used so that the soil does not reach a stronglyalkaline region of a pH of 11 or more, namely, in a pH region whereettringite is not generated, it is considered that a mineral other thanthe ettringite is generated by aluminum in the amorphous aluminumcompound, a silica component or a calcium component contained in thesoil being an object of treatment, and a component of a heavy metal orthe like contained in the soil or the insolubilizing material itself, asa result thereof the heavy metal or the like in the soil is immobilizedas a constituent of the mineral, and the excellent effects of the firstinvention of the present invention has been able to be achieved.

According to the detailed studies made by the present inventors, theamorphous aluminum compound is excellent in adsorbing ability of theheavy metal or the like when compared with the crystalline aluminumcompound, and therefore the amorphous aluminum compound easily adsorbsthe heavy metals or the like contained in the soil, in the surface ofthe soil, or in the insolubilizing material itself when added in thesoil or to the surface of the soil. Furthermore, it is considered thatin the process for the amorphous aluminum compound to change to becrystalline inside the soil, the amorphous aluminum compound takes in asilica component or a calcium component contained in the soil to form amineral with the adsorbed heavy metal or the like, and as a resultthereof, the heavy metal or the like has been able to be stablyinsolubilized. According to the studies made by the present inventors,the amorphous aluminum compound that characterizes the first inventionof the present invention has a function of insolubilizing a specifictoxic substance contained in the soil such as, for example, a heavymetal such as arsenic, selenium, cadmium, mercury, cyanogen, lead, andhexavalent chromium, and inorganic matter such as fluorine and boron andstably immobilizing the specific toxic substance contained in the soilin the treated matter.

The present inventors have mixed and cured the amorphous aluminumcompound and the soil so that the soil does not reach a stronglyalkaline region of a pH of 11 or more and have conducted a research onthe properties of the solidified matter after curing in order to confirmthe above-described function of the amorphous aluminum compound.Specifically, the X-ray diffraction for each of a sample of the soilonly, a sample after 1 week of curing, and the sample after 1 month ofcuring used for the above-described test has been measured. The obtainedresults of the X-ray diffraction measurement are shown in FIG. 2.Reference numeral 1 in the figure shows the X-ray diffraction for thesample of the soil only, reference numeral 2 in the figure shows theX-ray diffraction for the sample after 1 week of curing, and referencenumeral 3 in the figure shows the X-ray diffraction for the sample after1 month of curing. In addition, in the above-described tests, thecalcined gypsum was used together with the amorphous aluminum compound,and the reason for this is as follows. The components necessary for theinsolubilizing technology of the present invention that has been provedas a result of the studies are calcium, silica, and aluminum, however,among these components, the amount of the calcium component suppliedfrom the soil is extremely small as compared with the amorphous aluminumcompound that is positively added and the silica component that is notpositively added and supplied from the soil. On the other hand, thegypsum is a neutral material and therefore in the case where the gypsumis mixed and treated with the soil, the state of the soil does not reacha strongly alkaline region, and the treated matter can surely be made ina state where the calcium component is abundantly present, and thereforethe gypsum is added in conducting the above-described tests. Thus, inthe first invention of the present invention, it is also preferable thatthe constitution comprises the amorphous aluminum compound as a maincomponent and further the calcium component such as the gypsum thatshows acidity, neutrality, and a weak alkalinity of a pH of less than 11when the calcium component makes contact with the moisture contained inthe soil. Examples of the calcium component used in this case include atleast any one selected from the group consisting of calcium carbonate,calcium peroxide, calcium fluoride, calcium iodide, calcium phosphate,calcium chloride, calcium nitrate, calcium acetate, calcium citrate,calcium gluconate, calcium malate, and calcium lactate in addition tothe above-described gypsum. Moreover, in the case where the soil isacidic (the soil having a pH of 4 or less), calcium oxide and calciumhydroxide can also be used. The above-described gypsum is notparticularly limited, however it is preferable that the gypsum isdihydrate gypsum that can be used without conducting calcinationtreatment. Moreover, even in the case where there is a concern over thepresence of a heavy metal or the like attributable to the gypsum itselfsuch as waste gypsum, such gypsum can be used because such heavy metalscan also be immobilized stably in the treated matter.

As shown in FIG. 2, it has been confirmed that in the sample after 1week of curing and further the sample after 1 month of curing, a peakthat is clearly not attributable to the insolubilizing material, thegypsum used simultaneously, or the constituent of the soil appears near2θ=28.5°. Moreover, when the result of the sample after 1 week of curingand the result of the sample after 1 month of curing are compared, thepeak of the sample after 1 month of curing is higher than the peak ofthe sample after 1 week of curing regarding the peaks appeared around2θ=28.5°. These facts show that some crystalline compound (mineral) hasbeen generated in the treated matter by conducting the above-describedtreatment. In addition, from the results shown in FIG. 2, it has alsobeen able to confirm that the characteristic peaks that correspond toettringite (2θ=9.1° and 15.8°) do not appear.

The present inventors have conducted synthesis of crystalline compoundshaving various compositional formulas considering, from the resultsobtained above, the constituents of the insolubilizing material for aspecific toxic substance of the present invention and the soilcomponents obtained by adding and mixing the insolubilizing material tothe soil and have measured the X-ray diffraction for the obtainedcompounds. As a result thereof, it has been found that the obtainedcompound having a peak near 2θ=28.5° is any one of CaAl₂Si₆O₁₆.6H₂O,Ca(Si,Al)₁₆O₃₂.13H₂O, CaAl₂Si₇O₁₈.5.5H₂O, Ca₁₂Al₂Si₁₈O₅₁.18H₂O,CaAl₂Si₁₀O₂₄.7H₂O, (Ca,Na₂,K₂)Al₂Si₁₀O₂₄.7H₂O, CaAl₂Si₇O₁₈.6H₂O,CaAl₂Si₆O₁₆.4H₂O, Ca₃Al₂(SiO₄)(OH)₈, and Ca₃Al₂Si₃O₁₂. These coincidewith the chemical compositions of the mineral species, therefore it isconsidered that some crystalline compound (mineral) is generated by thetreatment conducted using the insolubilizing material for a specifictoxic substance of the present invention and as a result thereof thepeak has appeared near 2θ=28.5° in the X-ray diffraction.

As a result of the above-described studies, it has been proved that thecomponents necessary for the insolubilizing technology of the presentinvention are calcium, silica, and aluminum, however as describedpreviously, the amount of the calcium component is extremely small ascompared with the silica component supplied from the soil, and thereforeit is preferable that the insolubilizing material for a specific toxicsubstance of the first invention of the present invention comprises theamorphous aluminum compound and further the calcium component usedtogether with the amorphous aluminum compound. In the present invention,the specific calcium component that is used together with the amorphousaluminum compound may be any calcium component as exemplified previouslyas long as the calcium component showing acidity, neutrality, or a weakalkalinity of a pH of less than 11 when the calcium component makescontact with the moisture contained in the soil. The reason is becausewhen the calcium component that is used together with the amorphousaluminum compound is a compound as described above that does not reach apH 11 or more (strong alkalinity) when the calcium component makescontact with the moisture contained in the soil, the insolubilizingtreatment of the heavy metal or the like is made possible so that thesoil does not reach a pH of 11 or more, namely, in a state where theettringite is not generated in the case where the insolubilizingmaterial of the present invention is used. Moreover, even in the casewhere the heavy metal or the like attributable to the calcium componentto be used itself is present or in the case where there is a concernover the presence of a heavy metal or the like attributable to thecalcium component to be used itself, the heavy metal or the like issupposed to be stably immobilized in the treated matter when theinsolubilizing material for a specific toxic substance of the firstinvention of the present invention is used.

[Amorphous Aluminum Hydroxide]

According to further studies made by the present inventors, it isparticularly preferable to use amorphous aluminum hydroxide as anamorphous aluminum compound in order to achieve the object of the firstinvention of the present invention in a high level. Moreover, examplesof such a compound include volcanic ash soil and aluminum sludge that isgenerated at an anodic aluminum plant or an aluminum sash plant.Furthermore, surprisingly, it has been found that the remarkable effectsof the present invention are obtained by using the aluminum sludge as itis or the dehydrated and dried aluminum sludge without changing theproperties thereof in the present invention. According to the studiesmade by the present inventors, the aluminum sludge generated at theanodic aluminum plant or the aluminum sash plant has differentproperties depending on the process or the like, and it is difficult tospecify the properties, however at least a large amount of amorphousaluminum hydroxide is contained. The present inventors have found thatin the insolubilizing material of the first invention of the presentinvention, the material in which a large amount of such amorphousaluminum hydroxide is present is effective and usable, can insolubilizethe heavy metal or the like, and the effect of stably suppressing theelution of the heavy metal or the like including the re-elution afterthe insolubilization are obtained.

Specifically, by just adding and mixing the aluminum sludge containing alarge amount of amorphous aluminum hydroxide to the soil, or by justspraying the aluminum sludge containing a large amount of amorphousaluminum oxide to the surface of the soil, the elution of the heavymetal or the like from the treated matter is effectively suppressed, thetreated matter is neutral, and further the immobilized heavy metal orthe like is not re-eluted from the treated matter even when the treatedmatter is exposed to an acid condition such as an acid rain to saynothing of the case under a neutral condition. In the present invention,it is particularly preferable to use the aluminum sludge containingamorphous aluminum hydroxide as the amorphous aluminum compound thatcharacterizes the first invention of the present invention as it is orby dehydrating and drying the aluminum sludge without changing theproperties thereof. When such a material is used, more economicaltreatment is made possible. In the first invention of the presentinvention, it becomes necessary to use amorphous aluminum hydroxidecontained in the aluminum sludge so as not to be oxidized, which isdifferent from the technologies described in Patent Literatures 3 and 4.In addition, regarding the means in which amorphous aluminum hydroxideis not oxidized, any means that is currently conducted can appropriatelybe used. The measurement result of X-ray diffraction for the dehydratedand dried aluminum sludge is shown in FIG. 1.

It is considered that regarding the insolubilizing material for aspecific toxic substance of the first invention of the present inventionhaving the above-described constitution, although the detail is unclearas described previously, the amorphous aluminum compound adsorbs theheavy metal or the like contained in the soil, in the surface of thesoil, or in the insolubilizing material itself, thereafter takes in theheavy metal or the like to make a mineral, thereby the heavy metal canstably be insolubilized, and as a result thereof, the remarkable effectsof the first invention of the present invention have been obtained. Theremarkable effects of the present invention can be confirmed byconducting elution tests under a neutral condition or an acidiccondition as will be described later. Moreover, the amorphous aluminumcompound that is used in the first invention of the present invention isinsoluble to water, however it has been found that the amorphousaluminum compound is capable of functioning as a neutralizing agent bygently reacting with an alkali. Therefore, most of the soil or the likethat is generated on the spot shows alkalinity, however it has beenconfirmed that in the case where treatment is conducted with theinsolubilizing material for a specific toxic substance of the firstinvention of the present invention, the treated matter the pH of whichis effectively kept in neutral is obtained.

The insolubilizing material for a specific toxic substance of the firstinvention of the present invention can effectively be used by adding andmixing to the soil, however the effects of the first present inventionof the present invention are obtained and can simply be used also byspraying the insolubilizing material near the surface of the soil.

Next, preferable embodiments of the method for insolubilizing a specifictoxic substance of the first invention of the present invention isdescribed. The method for insolubilizing a specific toxic substance ofthe present invention is characterized in that treatment is conducted byadding and mixing or spraying the aforementioned insolubilizing materialfor a specific toxic substance of the first invention of the presentinvention to the soil, however it is preferable in the case to conductadding and mixing or spraying of the insoluble material according to thefollowing criteria. By doing in this way, the effects of the firstinvention of the present invention can sufficiently be obtained, andeconomical treatment is made possible. Namely, it is favorable that theaddition amount of the insolubilizing material of the first invention ofthe present invention to the soil is to make the amount of the amorphousaluminum compound or the derivative thereof as a main component of theinsolubilizing material for a specific toxic substance within a range of0.5 to 50 g per 1 kg of dried mass of the soil, and it is morepreferable that the addition amount of the insolubilizing material ofthe first invention of the present invention to the soil is to add andmix, or spray the amorphous aluminum compound or the derivative thereofwithin a range of 10 to 40 g per 1 kg of dried mass of the soil. It isnot preferable that the amount of the amorphous aluminum compound or thederivative thereof to be added and mixed, or sprayed is less than 0.5 gbecause the amount is too small and therefore it is difficult for thesecompounds to be uniformly dispersed in the soil. On the other hand, evenwhen the amorphous aluminum compound or the derivative thereof is addedand mixed, or sprayed in an amount exceeding 50 g, it is difficult toobtain further effects, the cost becomes high, which is not economical.Moreover, in the case where the insolubilizing material of the firstinvention of the present invention is added and mixed to the soil, watermay be added to the soil in an appropriate amount as necessary for thepurpose of making the mixing operation easy. It is preferable that thepH of the treated soil is made so as to be in a range of 5.6 to 8.6 inaddition to the above-mentioned criteria taking it into considerationthat the treated matter is thereafter utilized for landfill or the like,however when the insolubilizing material for a specific toxic substanceof the present invention is added and mixed by adjusting the amountthereof in the above-described manner, the pH value within theabove-described range can be achieved without particularly adjusting thepH thereafter. As a result thereof, in the case where the elution testof the heavy metal or the like is conducted, for example, for thereclaimed soil utilizing the treated matter, the elution of the heavymetal or the like can more surely be suppressed.

Second Invention of Present Invention

Next, the insolubilizing material for a specific toxic substance of thesecond invention of the present invention that also functions as asolidifying material (hereinafter, also referred to as “the secondinsolubilizing material for a heavy metal or the like of the presentinvention”) is described.

The present inventors have made further detailed studies based on theabove-described findings, and as a result thereof have found, first ofall, that it is effective to utilize the calcined gypsum to impartsolidifying performance to the insolubilizing material for a specifictoxic substance. The present inventors have found that when theamorphous aluminum compound and the derivative thereof (amorphousaluminum compound) in particular among the aluminum compounds is addedand mixed to the calcined gypsum, it becomes possible to provide aninsolubilizing material for a specific toxic substance with which: theelution of the heavy metal or the like can effectively be reduced; theheavy metal or the like is not re-eluted and is stably immobilized evenwhen the treated matter is exposed to the acidic condition such as anacid rain; more favorable strength is imparted to the soil; andfurthermore the treated matter is made neutral, and have reached thesecond invention of the present invention. In addition, the amorphouscompound or the derivative thereof may be an aluminum compound that isrecognized to be in an amorphous state by the X-ray diffraction.Moreover, in order to obtain excellent effects of the second inventionof the present invention, it is particularly preferable that theamorphous aluminum compound is added to the calcined gypsum in a rangeof 0.5 to 60 mass parts, further in a range of 15 to 50 mass partsrelative to 100 mass parts of the calcined gypsum. As will be describedlater, as the amorphous aluminum compound that is used in the presentinvention, the aluminum sludge that is generated at an anodized aluminumplant, an aluminum sash plant, or the like and most of which has beendisposed of can be utilized as it is or in a state where simpledehydration or air drying is conducted. Furthermore, the waste gypsumagainst which there is a concern over the presence of the heavy atom orthe like attributable to the material itself can effectively be utilizedas a material, and therefore the insolubilizing material for a specifictoxic substance of the second invention of the present invention becomesextremely economical in its material constitution.

Moreover, the insolubilizing material for a specific toxic substance ofthe second invention of the present invention comprising theabove-described constitution becomes an insolubilizing material in whichthe calcined gypsum and the amorphous aluminum compound or thederivative thereof are uniformly mixed, and therefore the efficiency ofthe treatment operation can markedly be improved in the case where theinsolubilizing material for a specific toxic substance of the secondinvention of the present invention is used.

Hereinafter, each material that constitutes the insolubilizing materialfor a specific substance of the second invention of the presentinvention is described.

(Gypsum)

As gypsum that is used in the second insolubilizing material for aspecific toxic substance of the present invention, calcined gypsumexcellent in the soil-solidifying performance is used. The calcinedgypsum is ½ hydrate of calcium sulfate [CaSO₄.½H₂O] and anhydride ofcalcium sulfate [CaSO₄], and the solidifying performance of the secondinsolubilizing material for a specific toxic substance of the presentinvention can further be improved by using the calcined gypsum. Namely,the calcined gypsum chemically reacts with the moisture in the soil toeasily change to dihydrate gypsum, and therefore the soil treated withthe calcined gypsum solidifies to have strength. Examples of thecalcined gypsum include β type hemihydrate gypsum, α type hemihydrategypsum, calcium sulfate anhydrite II, calcium sulfate anhydrite III, ora mixture thereof, and any of them can be used. The hydration rate ofcalcium sulfate anhydrite II is sluggish when compared with that ofother calcined gypsum, however calcium sulfate anhydrite II can be used.Natural gypsum, by-product gypsum, or waste gypsum may be used as rawmaterial gypsum of the calcined gypsum. Natural gypsum and by-productgypsum among these are low-cost materials and preferable, however it ismore preferable to use waste gypsum as a raw material takinghigher-level economy and effective use of resources into consideration.As described previously, according to the second insolubilizing materialfor a specific toxic substance of the present invention, even in thecase where there is a concern over the presence of the heavy metal orthe like attributable to the material itself such as waste gypsum, theheavy metal or the like is supposed to be stably immobilized in thetreated matter.

(Amorphous Aluminum Compound)

The present inventors consider the reason that the amorphous aluminumcompound that constitutes the insolubilizing material for a specifictoxic substance of the second invention of the present invention hasbeen able to effectively immobilize the heavy metal or the like in thetreated matter and to function as an excellent insolubilizing componentwith which the re-elution of the immobilized heavy metal or the like caneffectively be suppressed under both of a neutral condition and anacidic condition as follows from the verification results describedbelow. Namely, when the insolubilizing material for a specific toxicsubstance of the second invention of the present invention is used undera condition that soil containing the heavy metal or the like does notreach a strongly alkaline region of a pH of 11 or more, a mineral otherthan ettringite is generated by aluminum in the amorphous aluminumcompound, calcium in the gypsum, a calcium component or silica componentcontained in the soil as an object of treatment, and a metal or the likecontained in the soil or in the insolubilizing material itself, as aresult thereof, the heavy metal or the like in the mud is immobilized asa constituent of the mineral, and as a result thereof the excellenteffects of the second invention of the present invention has been ableto be achieved. According to the detailed studies made by the presentinventors, the amorphous aluminum compound is excellent in adsorbingability of the heavy metal or the like when compared with thecrystalline aluminum compound, and therefore the amorphous aluminumcompound easily adsorbs the heavy metal or the like contained in thesoil or the gypsum material that is a constituent of the solidifyingmaterial, when added into the soil. Furthermore, it is considered thatin the process for the amorphous aluminum compound to change to becrystalline in the soil, the amorphous aluminum compound takes in theadsorbed heavy metal or the like to form a mineral, and as a resultthereof, the heavy metal or the like has been able to be stablyinsolubilized. According to the studies made by the present inventors,the amorphous aluminum compound that characterizes the present inventionhas a function of insolubilizing a specific toxic substance contained inthe soil such as, for example, a heavy metal such as arsenic, selenium,cadmium, mercury, lead, and hexavalent chromium, and inorganic mattersuch as fluorine and boron and also has a function of stablyimmobilizing the specific toxic substance contained in the soil in thetreated matter.

The present inventors have mixed and cured the calcined gypsum, theamorphous aluminum compound, and the soil under a condition that thesoil does not reach a strongly alkaline region of a pH of 11 or more andhave conducted a research on the properties of the solidified matterafter curing in order to confirm the above-described function of theamorphous aluminum compound. Specifically, the X-ray diffraction foreach of a sample of the soil only, a sample after 1 week of curing, andthe sample after 1 month of curing used for the above-described test hasbeen measured. The obtained results of the X-ray diffraction measurementare shown in FIG. 2. Reference numeral 1 in the figure shows the X-raydiffraction for the sample of the soil only, reference numeral 2 in thefigure shows the X-ray diffraction for the sample after 1 week ofcuring, and reference numeral 3 in the figure shows the X-raydiffraction for the sample after 1 month of curing.

As shown in FIG. 2, it has been confirmed that in the sample after 1week of curing and further the sample after 1 month of curing, a peakthat is clearly not attributable to the insolubilizing material, or theconstituent of the soil appears near 2θ=28.5°. Moreover, when the resultof the sample after 1 week of curing and the result of the sample after1 month of curing are compared, the peak of the sample after 1 month ofcuring is higher than the peak of the sample after 1 week of curingregarding the peaks appeared around 2θ=28.5°. These facts show that somecrystalline compound (mineral) during the treatment has been generatedby conducting the above-described treatment. In addition, from theresults shown in FIG. 2, it has been confirmed that the characteristicpeaks that correspond to ettringite (2θ=9.1° and 15.8°) do not appear.

The present inventors have conducted synthesis of crystalline compoundshaving various compositional formulas considering, from the resultsobtained above, the constituents of the insolubilizing material for aspecific toxic substance of the second invention of the presentinvention and the soil components obtained by adding and mixing theinsolubilizing material to the soil and have measured the X-raydiffraction for the obtained compounds. As a result thereof, it has beenfound that the compound having a peak near 2θ=28.5° is any one ofCaAl₂Si₆O₁₆.6H₂O, Ca(Si,Al)₁₆O₃₂.13H₂O, CaAl₂Si₇O₁₈.5.5H₂O,Ca₁₂Al₂Si₁₈O₅₁.18H₂O, CaAl₂Si₁₀O₂₄.7H₂O, (Ca,Na₂,K₂)Al₂Si₁₀O₂₄.7H₂O,CaAl₂Si₇O₁₈.6H₂O, CaAl₂Si₆O₁₆.4H₂O, Ca₃Al₂(SiO₄)(OH)₈, and Ca₃Al₂Si₃O₁₂.These coincide with the chemical compositions of the mineral species,therefore it is considered that some crystalline compound (mineral) isgenerated by the treatment conducted using the insolubilizing materialof the second invention of the present invention and as a result thereofthe peak derived from the mineral has appeared near 2θ=28.5° in theX-ray diffraction.

[Amorphous Aluminum Hydroxide]

According to further studies made by the present inventors, it has beenfound that it is particularly preferable to use amorphous aluminumhydroxide as an amorphous aluminum compound in order to achieve theobject of the second invention of the present invention in a high level.Examples of such a compound include an aluminum component contained involcanic ash soil and aluminum sludge that is generated at an anodicaluminum plant or an aluminum sash plant. Furthermore, surprisingly, theremarkable effects of the second present invention of the presentinvention are obtained by using the aluminum sludge as it is ordehydrated and the dried aluminum sludge without changing the propertiesthereof together with the gypsum to make a solidifying material in thesecond invention of the present invention. According to the studies madeby the present inventors, the aluminum sludge that is generated at theanodic aluminum plant or the aluminum sash plant has differentproperties depending on the process or the like, and it is difficult tospecify the properties, however at least a large amount of amorphousaluminum hydroxide is contained. The present inventors have found thatin the insolubilizing material for a specific toxic substance of thesecond invention of the present invention, the material in which a largeamount of such amorphous aluminum compound is present is effective, caninsolubilize the heavy metal or the like, and the effect of stablysuppressing the elution of the heavy metal or the like including there-elution after the insolubilization is obtained.

Specifically, in the second invention of the present invention, by usingthe aluminum sludge containing a large amount of amorphous aluminumhydroxide together with the calcined gypsum and just adding and mixingthe aluminum sludge containing a large amount of amorphous aluminumhydroxide and the calcined gypsum to the soil, the elution of the heavymetal or the like from the treated matter is effectively suppressed, thetreated matter is neutral, further the immobilized heavy metal or thelike is not re-eluted from the treated matter even when the treatedmatter is exposed to an acid condition such as an acid rain to saynothing of the case under a neutral condition, and furthermore thetreated matter is made so as to have solidified strength to the extentin which handling is easy at the time of transportation or landfill evenwhen the soil is the sludge generated by waste water treatment or themud such as construction surplus soil. Particularly in the presentinvention, the aluminum sludge containing amorphous aluminum hydroxideas an amorphous aluminum compound that constitutes the second inventionof the present invention can be used as it is or by dehydrating anddrying the aluminum sludge without changing the properties thereof, andby doing in this way, the economical treatment in terms of materials tobe used is made possible. In the second invention of the presentinvention, the above-described things means that it is necessary to useamorphous aluminum hydroxide contained in the aluminum sludge so as notto be oxidized, which is different from the technologies described inPatent Literatures 1 and 2. In addition, regarding the means with whichamorphous aluminum hydroxide is not oxidized, any means that iscurrently conducted can appropriately be used. The measurement result ofX-ray diffraction for the dehydrated and dried aluminum sludge is shownin FIG. 1.

The insolubilizing material for a specific toxic substance of the secondinvention of the present invention comprises the above listed amorphousaluminum compound externally added to the calcined gypsum in a range of0.5 to 60 mass parts relative to 100 mass parts of the calcined gypsum.Namely, with the insolubilizing material for a specific toxic substanceof the second invention of the present invention in which the additionamount of the amorphous aluminum compound relative to 100 mass parts ofthe calcined gypsum is less than 0.5 mass parts, the effect ofinsolubilizing the heavy metal or the like cannot sufficiently beobtained when blended in the soil as a solidifying material, and on theother hand the insolubilizing material for a specific toxic substance ofthe second invention of the present invention in which the additionamount of the amorphous aluminum compound relative to 100 mass parts ofthe calcined gypsum is mixed in an amount exceeding 60 mass partsbecomes high in the material cost and becomes not economical. It is morepreferable that the amorphous aluminum compound is added to the calcinedgypsum in a range of 15 to 50 mass parts relative to 100 mass parts ofcalcined gypsum.

It is preferable that the insolubilizing material for a specific toxicsubstance of the second invention of the present invention having theabove-described constitution and functions also as a solidifyingmaterial is utilized particularly in the case of conducting solidifyingtreatment by adding and mixing the insolubilizing material to the mud,and the aforementioned remarkable effects of the present can beobtained. It is considered that the reason for this is, although thedetail is unclear as described previously, that the amorphous aluminumcompound that is contained in the insolubilizing material together withthe gypsum such as calcined gypsum adsorbs the heavy metal or the likein the soil to thereafter make a mineral from the heavy metal or thelike in the soil, thereby the heavy metal has been able to stably beinsolubilized. The remarkable effects of the second invention of thepresent invention obtained by the insolubilizing material for a specifictoxic substance obtained by adding the amorphous aluminum compound tothe gypsum can be confirmed by conducting an elution test under aneutral condition or an acidic condition. Moreover, the amorphousaluminum compound that is used in the second invention of the presentinvention is insoluble to water, however it has been found that theamorphous aluminum compound is capable of functioning as a neutralizingagent by gently reacting with an alkali. Therefore, most of the mud thatis generated on the spot shows alkalinity, however it has been confirmedthat in the case where the mud is solidified with the secondinsolubilizing material for a specific toxic substance of the presentinvention, the treated matter the pH of which is effectively maintainedin neutral is obtained.

Next, preferable embodiments of the method for improving soil of thepresent invention using the insolubilizing material for a specific toxicsubstance of the second invention of the present invention thatfunctions also as a solidifying material is described. The method forimproving soil of the second invention of the present invention ischaracterized in that solidifying treatment is conducted simultaneouslywith the insolubilization of the heavy metal or the like by adding andmixing the second insolubilizing material for a specific toxic substanceof the present invention to the soil. It is preferable to conduct addingand mixing of the insolubilizing material in the case by the followingcriteria. By doing in this way, the effects of the present invention cansufficiently be obtained, and economical treatment is made possible.Namely, regarding the addition amount of the second insolubilizingmaterial for a specific toxic substance of the present invention,depending on the water content ratio of the soil or the requiredsolidification strength of the treated soil, it is preferable that 30 to200 kg of the insolubilizing material for a specific toxic substance per1 m³ of the soil containing a specific toxic substance is added andmixed. By doing in this way, the elution of the heavy metal or the likeis suppressed, and the cone index after the solidifying material of thepresent invention is added and mixed evenly to the soil, solidificationis conducted, and the resultant mixture is cured for 1 day becomes 100kN/m² or more, preferably 150 kN/m² or more, more preferably 200 kN/m²or more. It is preferable that the pH of the solidified soil is made soas to be in a range of 5.6 to 8.6 in addition to the above-mentionedcriteria taking it into consideration that the treated matter isthereafter utilized for landfill or the like, however the secondinsolubilizing material for a specific toxic substance of the presentinvention is added and mixed by adjusting the amount in theabove-described manner to achieve the pH of the solidified soil. As aresult thereof, the elution of the heavy metal or the like from the soilcan more surely be suppressed at a place where the treated matter isutilized for landfill.

In carrying out the method for improving soil of the second invention ofthe present invention, when water is sprayed to the soil in advance toimpart a certain extent of fluidity to the soil, and thereafter thesecond insolubilizing material for a specific toxic substance of thepresent invention is added and mixed to the soil, the mixing operationbecomes easy. The second insolubilizing material for a specific toxicsubstance of the present invention has soil-solidifying performance, andtherefore the treated matter is solidified to the extent that handlingis easy at the time of transportation or landfill even in the case wherethe treatment is conducted after imparting the fluidity to the soil byspraying water to the soil as described above. Therefore, in carryingout the method for improving soil of the second invention of the presentinvention to the sludge that is generated by waste water treatment orthe mud such as surplus soil waste from construction, treatment may beconducted adding and mixing the second insolubilizing material for aspecific toxic substance of the present invention to the mud withoutdehydration or the like.

[Test Method Used in Present Invention]

The measurement of each value described above was carried out by themethod described hereinafter in accordance with each test method shownhereinafter.

(1) Test Method for Water Content: In Accordance with “Test Method forWater Content of Soils JIS A1203”.

The water content w (%) is calculated by the following equation.

w=(m _(a) −m _(b))×100/(m _(b) −m _(c))

-   -   m_(a): mass of sample and vessel (g)    -   m_(b): mass of furnace-dried sample and vessel (g)    -   m_(e): mass of vessel (g)

(2) Elution Test of the Ministry of Environment Notification No. 18(2003) (Hereinafter Also Referred to as “No. 18 Test”

The soil to be an object is dried, passed through a 2 mm sieve, andfurthermore, using water as a solvent, 10 times the amount of water tothe passed dried soil is added to prepare a test sample. The test sampleis mixed by shaking at 200 times/min with a shaking width of 4 to 5 cmfor 6 hours continuously. Thereafter, centrifugal separation andfiltration were conducted, and then the obtained filtrate was used as asample for measurement. Metal analysis in the sample was conducted inaccordance with the methods for respective metals standardized by JIS.

(3) Long Term Stability Test

The elution test in an acidic condition was conducted in the same manneras described above except that the above-described water as a solventwas changed to a 0.769 mmol/L sulfuric acid aqueous solution (measuredpH value=2.9). The reason that the elution test was conducted in theabove-described condition using a sulfuric acid solution as a solvent asdescribed herein is that the acid rain occurred in the natural worldwhere the treated matter is left to stand was supposed. Specifically,the above-described condition was calculated out as the case where thetreated matter is supposed to be exposed to an environment with anannual rainfall of 2000 mm having a pH of 4.0 for 100 years [inaccordance with Geo-Environmental Protection Center Technical Standard“Leaching Test for Heavy Metals-Immobilized Soil Using Acid or AlkalineSolution” (hereinafter referred to as the “Acid Addition ElutionTest”)].

(4) pH Test: In Accordance with “the Method for pH of Suspended SoilsJGS0211”

A sample is placed in a beaker, and water is added so that the massratio of water (including water in the sample) to the dried mass of thesample becomes 5. The sample is suspended with a stirring rod and isleft still for 30 minutes or more and 3 hours or less to make a samplesolution. The pH is measured by a glass electrode pH meter after thesample solution in the beaker is stirred.

(5) Cone Index Test: In Accordance with “Test Method for Cone Index ofCompacted Soils JIS A1228”

First of all, a soil sample that is passed through a 9.5 mm sieve isplaced in a mold having an inner diameter of 10 cm in accordance withJIS A1210 and is rammed down in three layers with 25 times per 1 layerusing a rammer having a mass of 2.5 kg. Next, a cone penetrometer isstood vertically in the center of an upper end face of a test sample andis penetrated at a rate of 1 cm/sec, and the penetration resistanceforces are determined from the readings of a load measuring apparatuswhen the tip of the cone is penetrated to 5 cm, 7.5 cm, and 10 cm fromthe end face of the test sample respectively. The cone index q_(c)(kN/m²) is calculated out by the following equation from the averagepenetration resistance Q_(c) (N) and the base area A (cm²) of the tip ofthe cone.

q _(c) =Q _(c)×10/A

EXAMPLES

Next, the present invention will be described specifically givingExamples of the present invention and Comparative Examples.

First Invention of Present Invention <Preparation of Evaluation Sample>

Soil that was dried to become a constant weight in a drying furnace at110° C.±5° C. was prepared. And arsenic and fluorine were added to thesoil to prepare simulated polluted soil so that the elution amount ofarsenic became 0.1 mg/L and the elution amount of fluorine became 2.5mg/L.

<Evaluation 1>

Insolubilizing arsenic and fluorine in the soil using the insolubilizingmaterial for a specific toxic substance of the first invention of thepresent invention was conducted, as Examples 1-1 to 1-4, by adjustingthe water content ratio of 1 kg of the simulated polluted soil obtainedabove to 40% and adding and mixing amorphous aluminum hydroxide to beadded changing the amounts thereof as shown in Table 1 respectively tothe simulated polluted soil. Moreover, the example in which amorphousaluminum hydroxide was not used was denoted as Comparative Example 1-1,and the examples in which aluminum hydroxide and aluminum chloride wererespectively used in place of amorphous aluminum hydroxide used inExamples and treatment was conducted by adding and mixing 10 g of thesecompounds respectively to 1 kg of the above-described dried simulatedpolluted soil were denoted as Comparative Examples 1-2 and 1-3respectively.

TABLE 1 Sample Preparation Addition amount Kind (g) Example 1-1Amorphous aluminum hydroxide 0.5 Example 1-2 Amorphous aluminumhydroxide 10 Example 1-3 Amorphous aluminum hydroxide 40 Example 1-4Amorphous aluminum hydroxide 50 Comparative Example 1-1 Not Added —Comparative Example 1-2 Aluminum hydroxide 10 Comparative Example 1-3Aluminum chloride 10

Specifically, insolubilizing treatment was conducted by adding a desiredamount of each of the insolubilizing materials for a specific toxicsubstance of the above-described Examples and Comparative Examples tothe simulated soil as an object of treatment and thereafter sufficientlykneading the resultant mixture. After 1 day of curing after thetreatment, the elution amount of arsenic and fluorine from the treatedsoil and the pH of the treated soil were measured. The measurement atthe time was conducted by the afore-mentioned method. The obtainedresults are shown in Table 2. As shown in Table 2, it was confirmed thatthe elution of arsenic and fluorine was suppressed in any of the caseswhere the insolubilizing material for a specific toxic substance ofExamples was used. Furthermore, it was confirmed that the treated matterwas neutral. Moreover, regarding the treated matter for which theinsolubilizing material for a specific toxic substance of Examples ofthe first invention of the present invention was used, when the treatedmatter to which the above-described treatment had been conducted wasleft to stand for six month and then the elution amount of arsenic andthe elution amount of fluorine were measured in the same manner asdescribed above, it was confirmed that the measured values shown inTable 2 were maintained.

TABLE 2 Elution Test Results Elution amount (mg/L) Arsenic Fluorine pH(—) Example 1-1 0.050 1.25 7.45 Example 1-2 0.005 0.72 7.30 Example 1-3<0.005 0.45 7.25 Example 1-4 <0.005 0.41 7.25 Comparative Example 1-10.10 2.50 7.50 Comparative Example 1-2 0.09 2.48 7.20 ComparativeExample 1-3 0.09 2.47 5.90 Environmental standard 0.01 or less 0.8 orless 5.8-8.6

<Evaluation 2>

Furthermore, treatment of insolubilizing the following heavy metals wasconducted in the same manner as in Example 1-2 using amorphous aluminumhydroxide being the insolubilizing material for a specific toxicsubstance of Examples, and the obtained treated matter was evaluated byconducting the elution test. Specifically, lead, hexavalent chromium,and selenium were added to prepare simulated polluted soil in which theelution amount of lead was adjusted to 0.1 mg/L, the elution amount ofhexavalent chromium was adjusted to 0.5 mg/L, and the elution amount ofselenium was adjusted to 0.1 mg/L, and the water content ratio wasadjusted to 40%. And the insolubilizing material for a specific toxicsubstance was added and kneaded in the soil in the same manner as inExample 1-2 in Evaluation 1, and thereafter the elution test wasconducted. Moreover, the treatment similar to Example 1-2 was conductedusing each of the afore-mentioned compounds that were used inComparative Examples 1-1 to 1-3. As a result thereof, regarding any ofthe metals, it was confirmed that the effect of insolubilization wasclearly obtained when compared with Comparative Examples in the casewhere the insolubilizing material for a specific toxic substance ofExample 1-2 was used.

TABLE 3 Elusion Test Results Elution amount (mg/L) Hexavalent Leadchromium Selenium Example 1-2 <0.005 0.02 <0.005 Comparative Example 1-10.10 0.50 0.10 Comparative Example 1-2 0.08 0.50 0.09 ComparativeExample 1-3 0.09 0.49 0.09 Environmental Standard 0.01 or less 0.05 orless 0.01 or less

Example 1-5 and Comparative Example 1-4

An insolubilizing material for a specific toxic substance of Example 1-5of the first invention was prepared by adding 100 mass parts of calcinedgypsum to 25 mass parts of aluminum sludge containing a large amount ofamorphous aluminum hydroxide as an amorphous aluminum compound for thepurpose of adding a calcium component and giving a solidifying function.The elution test of heavy metals after treatment was conducted using acommercial cement solidifying material for comparison. Using eachmaterial, to 1600 kg (1 m³) of the simulated mud of an object oftreatment, 100 kg of each material was added, thereafter treatment wasconducted by sufficiently kneading the resultant mixture. Thereafter,curing was conducted for 60 days. And the No. 18 test and the acidaddition elution test were conducted collecting a sample on the firstday, on the 30th day, and on the 60th day respectively. The obtainedtest results are shown in FIG. 3.

As it is clear from FIG. 3, it was confirmed that the elution amountswere clearly different between the case where the insolubilizingmaterial for a specific toxic substance of Example 1-5 of the firstinvention was used and the case where the solidifying material ofComparative Example 1-4 was used, and that the elution amount offluorine was markedly smaller in the case where the insolubilizingmaterial for a specific toxic substance of Example 1-5 was used than inthe case where the solidifying material of Comparative Example 1-4 wasused. Moreover, in the case where the insolubilizing material for aspecific toxic substance of Example 1-5 was used, the elution amount asa result of conducting the elution test using a sulfuric acid solutionas a solvent was rather small as compared with the case of the elutionby water at an initial stage after the treatment. On the other hand, inthe case where the solidifying material of Comparative Example 1-4 wasused, the elution amount clearly became greater in the acidic conditionusing a sulfuric acid solution than in the case where water was used asa solvent, and it was shown that there was a problem of re-eluting theimmobilized heavy metal or the like in particular.

Example 1-6

An insolubilizing material for a specific toxic substance of Example 1-6was prepared by adding 100 mass parts of calcined gypsum using, as a rawmaterial, waste gypsum in which fluorine was recognized to be containedto 25 mass parts of aluminum sludge containing a large amount ofamorphous aluminum hydroxide as an amorphous aluminum compound for thepurpose of adding a calcium component and giving a solidifying function.The insolubilizing material for a specific toxic substance of Example1-6 was sprayed on the surface of the soil to cure for 60 days. And theelution test was conducted in the same manner as in Example 1-5sampling, on the first day and on the 60th day, a portion of theinsolubilizing material from the surface of the soil where theinsolubilizing material was sprayed. As a result thereof, it wasconfirmed that the elution amount from the sample on the 60th day wasclearly reduced as compared with the elution amount from the sample onthe first day.

Second Invention of Present Invention

Next, the present invention will be described specifically givingExamples of the second invention of the present invention andComparative Examples. In addition, the “parts” in the followingdescription are based on mass unless otherwise noted.

Preparation of Evaluation Samples of Examples 2-1 to 2-4 and ComparativeExample 2-1

The insolubilizing materials for a specific toxic substance of Examplesand Comparative Example each having a combination shown in Table 4 usingcalcined gypsum and an amorphous aluminum compound were prepared. As thecalcined gypsum, pulverized and calcined waste gypsum was used for eachinsolubilizing material. And as the amorphous aluminum compound,amorphous aluminum hydroxide (a chemical agent) was used.

TABLE 4 Sample Preparation Combination (parts) Calcined gypsum Amorphousaluminum hydroxide Example 2-1 100 0.5 Example 2-2 100 15 Example 2-3100 50 Example 2-4 100 60 Comparative 100 0 Example 2-1

<Evaluation 1>

The evaluation was conducted using simulated polluted mud in which thewater content ratio was adjusted to 40% and arsenic and fluorine wereadded to adjust the elution amount of arsenic to 0.1 mg/L and adjust theelution amount of fluorine to 2.5 mg/L. And operations of insolubilizingarsenic and fluorine in the simulated polluted mud were conductedrespectively using: insolubilizing materials of Examples 2-1 to 2-4 eachobtained by adding amorphous aluminum hydroxide to gypsum so as to havea combination as shown in Table 4 by changing the amount of amorphousaluminum hydroxide; and a solidifying material of Comparative Example2-1 in which the amorphous aluminum compound was not contained.

Specifically, to 1 m³ of the simulated mud of an object of treatment,100 kg of each of the insolubilizing materials for a specific toxicsubstance of Examples or the solidifying material of Comparative Examplewas added, and thereafter insolubilizing treatment was conducted bysufficiently kneading the resultant mixture. After curing of 1 day afterthe treatment, the elution amount of arsenic and the elution amount offluorine from the mud in the No. 18 test and the solidification strength(cone index) were measured respectively. The measurement at the time wasconducted by the aforementioned method. The obtained results are shownin Table 5.

As shown in Table 5, it was able to be confirmed from the elution testresults for the treated matter in the case where the insolubilizingmaterial for a specific toxic substance of Examples of the secondinvention of the present invention was used that the elution of arsenicand fluorine was suppressed by using the insolubilizing material for aspecific toxic substance of Examples and the insolubilizing material fora specific toxic substance of Examples was useful as an insolubilizingmaterial for a specific toxic substance. Furthermore, it was confirmedthat the second insolubilizing material for a specific toxic substanceof the present invention was useful also as a solidifying material. Morespecifically, it was found that the solidification strength (cone index)of the treated matter was in an extent that makes handling easy, hadstrength of a state where the treated matter was easy to be reusable,and had a greater cone index value when compared with the case where thesolidifying material of Comparative Example in which amorphous aluminumhydroxide was not contained was used and therefore the treated matterhaving a higher strength was obtained. This means that the secondinsolubilizing material for a specific toxic substance of the presentinvention using an amorphous aluminum compound was more useful also as asolidifying material when compared with a conventional gypsumsolidifying material. Moreover, the treated matter to which theabove-described treatment had been conducted was left to stand for 6months, and the elution amount of arsenic and the elution amount offluorine in the No. 18 test were measured respectively in the samemanner as described above. As a result thereof, it was confirmed thatregarding the treated matter obtained by the solidifying material ofExamples of the second invention of the present invention, the measuredvalues shown in Table 5 were maintained and that the elution of theheavy metal or the like in the case where the treated matter was usedfor landfill or the like can effectively be suppressed. Furthermore, thepH of the treated matter is in a neutral region, and also from thisstandpoint, landfill treatment considering environmental conservationbecomes possible.

TABLE 5 Results of Evaluation 1 (Elution Test Results-1) Cone Elutionamount (mg/L) index Arsenic Fluorine (kN/m³) pH (—) Example 2-1 0.0351.20 210 7.15 Example 2-2 0.006 0.74 240 7.10 Example 2-3 <0.005 0.49300 7.04 Example 2-4 <0.005 0.45 320 7.04 Comparative Example 2-1 0.082.50 205 7.20 Environmental standard 0.01 or less 0.8 or less — 5.8-8.6

<Evaluation 2>

Furthermore, evaluation was conducted by conducting the elution test forrepresentative heavy metals using the insolubilizing material for aspecific toxic substance of Example 2-2 and the solidifying material ofComparative Example 2-1. Specifically, lead, hexavalent chromium, andselenium were added to prepare simulated polluted mud in which theelution amount of lead was adjusted to 0.1 mg/L, the elution amount ofhexavalent chromium was adjusted to 0.5 mg/L, and the elution amount ofselenium was adjusted to 0.1 mg/L, then an insolubilizing material for aspecific toxic substance or a solidifying material was added and kneadedin the simulated mud in the same manner as in Evaluation 1, andthereafter the elution test was conducted. As a result thereof, as shownin Table 6, regarding any of the metals, it was found that the effect ofcapable of insolubilizing these metals was clearly obtained in the casewhere the insolubilizing material for a specific toxic substance ofExample 2-2 was used when compared with the case where the solidifyingmaterial of Comparative Example 2-1 was used.

TABLE 6 Results of Evaluation 2 (Elution Test Results-2) Elution amount(mg/L) Hexavalent Lead chromium Selenium Example 2-2 <0.005 0.025 <0.005Comparative Example 2-1 0.085 0.450 0.085 Environmental standard 0.01 orless 0.05 or less 0.01 or less

Example 2-5 and Comparative Example 2-2

An insolubilizing material for a specific toxic substance of Example 2-5was prepared at a rate of 25 mass parts of aluminum sludge containing alarge amount of amorphous aluminum hydroxide as an amorphous aluminumcompound to 100 mass parts of calcined gypsum. The elution test of heavymetals was conducted using a commercial cement solidifying material forcomparison. Using these materials, to 1 m³ of the simulated mud of anobject of treatment, 100 kg of the solidifying material was added,thereafter treatment was conducted by sufficiently kneading theresultant mixture. Thereafter, curing was conducted for 60 days. And theNo. 18 test and the acid addition elution test were conducted collectinga sample on the first day, on the 30th day, and on the 60th dayrespectively. The obtained test results are shown in FIG. 3.

As it is clear from FIG. 3, it was confirmed that the elution amountswere clearly different between the case where the insolubilizingmaterial for a specific toxic substance of Example 2-5 was used and thecase where the solidifying material of Comparative Example 2-2 was used,and that the elution amount of fluorine was markedly smaller in the casewhere the insolubilizing material for a specific toxic substance ofExample 2-5 was used than in the case where the solidifying material ofComparative Example 2-2 was used. Moreover, in the case where theinsolubilizing material for a specific toxic substance of Example 2-5was used, the elution amount as a result of conducting the elution testusing a sulfuric acid solution as a solvent was rather small as comparedwith the case of the elution by water at an initial stage after thetreatment. On the other hand, in the case where the solidifying materialof Comparative Example 2-2 was used, the elution amount clearly becamegreater in the acidic condition using a sulfuric acid solution than inthe case where water was used as a solvent, and it was shown that therewas a problem of re-eluting the immobilized heavy metal or the like inparticular.

INDUSTRIAL APPLICABILITY First Invention of Present Invention

Application examples of the present invention include an insolubilizingmaterial for a specific toxic substance suitable for soil treatmentcapable of surely insolubilizing a heavy metal or the like contained inthe soil or near the surface of the soil; without re-elution of theinsolubilized heavy metal or the like from the treated matter even whenthe treated matter is exposed to rain or an acid rain after theinsolubilization; capable of stably insolubilizing the heavy metal orthe like utilizing a component contained in the soil; and stably makingthe treated matter neutral. Application examples of the presentinvention further include an economically excellent insolubilizingmaterial for a specific toxic substance that makes it possible toeffectively utilize waste gypsum and aluminum sludge both of whichmostly become waste, and the utilization is expected, and since thetreatment method using the insolubilizing material is extremely simple,the utilization is expected.

Second Invention of Present Invention

Application examples of the present invention include an insolubilizingmaterial for a specific toxic substance suitable for soil treatmentcapable of surely insolubilizing a heavy metal or the like contained inthe soil; without re-elution of the insolubilized heavy metal or thelike from the treated matter even when the treated matter is exposed torain or an acid rain after the insolubilization; capable of stablyinsolubilizing the heavy metal or the like in the soil; further capableof also imparting strength to the soil by solidification, and stablymaking the treated matter neutral. Application examples of the presentinvention further include an economically excellent insolubilizingmaterial for a specific toxic substance that makes it possible toeffectively utilize waste gypsum and aluminum sludge both of whichmostly become waste, and the utilization is expected.

1. An insolubilizing material for a specific toxic substance to be usedso that soil does not reach a strongly alkaline region of a pH of 11 ormore, the insolubilizing material for a specific toxic substancecomprising an amorphous aluminum compound or a derivative thereof as amain component, wherein the amorphous aluminum compound or thederivative thereof is amorphous aluminum hydroxide or a derivativethereof.
 2. An insolubilizing material for a specific toxic substance tobe used so that soil does not reach a strongly alkaline region of a pHof 11 or more, the insolubilizing material for a specific toxicsubstance comprising an amorphous aluminum compound or a derivativethereof as a main component, wherein the insolubilizing material for aspecific toxic substance further comprises a calcium componentexhibiting acidity, neutrality, or weak alkalinity of a pH of less than11 when the calcium component makes contact with moisture contained inthe soil.
 3. An insolubilizing material for a specific toxic substanceto be used so that soil containing a specific toxic substance does notreach a strongly alkaline region of a pH of 11 or more, theinsolubilizing material for a specific toxic substance comprising anamorphous aluminum compound or a derivative thereof as a main component,wherein the insolubilizing material for a specific toxic substancefurther comprises calcined gypsum, and the insolubilizing material for aspecific toxic substance comprising the calcined gypsum is obtained byadding and mixing, to the calcined gypsum, the amorphous aluminumcompound or the derivative thereof in a range of 0.5 to 60 mass partsrelative to 100 mass parts of the calcined gypsum.
 4. The insolubilizingmaterial for a specific toxic substance according to claim 2, whereinthe amorphous aluminum compound is amorphous aluminum hydroxide.
 5. Theinsolubilizing material for a specific toxic substance according toclaim 1, wherein the amorphous aluminum compound or the derivativethereof, or the amorphous aluminum hydroxide or the derivative thereofis derived from aluminum sludge and is to be used as it is; or obtainedby dehydrating and drying, without changing the properties, an amorphousaluminum compound or a derivative thereof, or amorphous aluminumhydroxide or a derivative thereof derived from aluminum sludge.
 6. Theinsolubilizing material for a specific toxic substance according toclaim 1, wherein the specific toxic substance is at least any oneselected from the group consisting of cadmium and compounds thereof,hexavalent chromium compounds, cyanides, mercury and compounds thereof(including alkyl mercury compounds), selenium and compounds thereof,lead and compounds thereof, arsenic and compounds thereof, fluorine andcompounds thereof, and boron and compounds thereof.
 7. Theinsolubilizing material for a specific toxic substance according toclaim 2, wherein the calcium component is at least any one selected fromthe group consisting of gypsum dihydrate, calcium carbonate, calciumperoxide, calcium fluoride, calcium iodide, calcium phosphate, calciumchloride, calcium nitrate, calcium acetate, calcium citrate, calciumgluconate, calcium malate, and calcium lactate.
 8. The insolubilizingmaterial for a specific toxic substance according to claim 3, whereinthe insolubilizing material for a specific toxic substance is obtainedby adding and mixing, to the calcined gypsum, the amorphous aluminumcompound and the derivative thereof in a range of 15 to 50 mass partsrelative to 100 mass parts of the calcined gypsum.
 9. A method forinsolubilizing a specific toxic substance, the method comprisingconducting treatment to soil so that the soil does not reach a stronglyalkaline region of a pH of 11 or more by adding and mixing, or sprayingto the soil the insolubilizing material for a specific toxic substanceaccording to claim 1 to insolubilize the specific toxic substance. 10.The method for insolubilizing a specific toxic substance according toclaim 9, the method comprising adding and mixing, or spraying to thesoil the amorphous aluminum compound or the derivative thereof, or theamorphous aluminum hydroxide or the derivative thereof being a maincomponent of the insolubilizing material for a specific toxic substancewithin a range of 0.5 to 50 g per 1 kg on a dry mass basis of the soil.11. The method for insolubilizing a specific toxic substance accordingto claim 9, the method comprising adding and mixing, or spraying to thesoil the amorphous aluminum compound and the derivative thereof, or theamorphous aluminum hydroxide or the derivative thereof being a maincomponent of the insolubilizing material for a specific toxic substancewithin a range of 10 to 40 g per 1 kg on a dry mass basis of the soil.12. The method for insolubilizing a specific toxic substance accordingto claim 9, wherein the specific toxic substance to be insolubilized isattributable to the soil or a constituent of the insolubilizingmaterial.
 13. The method for insolubilizing a specific toxic substanceaccording to claim 12, wherein the constituent of the insolubilizingmaterial is a calcium component.
 14. A method for improving soil,comprising conducting treatment to the soil containing a specific toxicsubstance so that the soil does not reach a strongly alkaline region ofa pH of 11 or more by adding and mixing to the soil the insolubilizingmaterial for a specific toxic substance functioning also as asolidifying material according to claim
 3. 15. The method for improvingsoil according to claim 14, comprising adding and mixing to the soil theinsolubilizing material for a specific toxic substance within a range of30 to 200 kg per 1 m³ of the soil containing a specific toxic substance.